A lactic acid bacterium has high ability to utilize a sugar source and utilizes glucose or a monosaccharide to perform lactic acid fermentation. In general, however, the lactic acid bacterium cannot ferment fructan which is an indigestible polysaccharide.
Fructan is an indigestible polysaccharide contained in a particularly large amount in garlic, rakkyo, and the like, and contents of the fructan in dried garlic and rakkyo are about 80% and about 70%, respectively.
Therefore, to increase the added value of garlic and rakkyo, an attempt has been made to directly ferment fructan contained at a high concentration (in particular, garlic), but has not succeeded.
In particular, garlic is expected to be used efficiently, and developments to use a variety of fermentations have been performed. Examples thereof include a case of carrying out fermentation by adding a small amount of garlic in a production process of wine (Patent Literature 1) and a case of carrying out fermentation by adding a large amount of a sugar to a small amount of garlic (Patent Literature 2).
Examples thereof further include a case of carrying cut fermentation using a ‘koji mold’ after deactivation of endogenous enzymes of garlic by heating (Patent Literature 3) and a case of carrying out lactic acid fermentation and propionic acid fermentation after heating and crushing garlic (Patent Literature 4).
However, none of the cases is a ‘technology for direct fermentation without a heating treatment or an enzymatic treatment’ of ‘fructan’ contained in garlic at a high concentration.
It should be noted that, with regard to physiological functions of garlic and rakkyo, many reports have been made on efficacy of an organic sulfur compound and saponin, but few reports have been made on fructan which accounts for a large percentage.
Therefore, it has been expected to develop a technology for giving high functionality or a technology for efficient use by fermenting fructan contained therein. In particular, an application to a ‘lactic acid fermented food,’ which is expected to have significantly high functionality, has been expected.